1. Field of the Invention
The invention concerns a circuit arrangement for the wireless transmission of control signals to the control paths of controlled semiconductor valves, particularly of thyristors, which are preferably used in a rectifier for high voltage. Specifically the invention concerns firing of thyristors used in a high voltage rectifier circuit by means of modulated control signals from a transmitter which are received by receivers associated with each thyristor.
2. Description of the Prior Art
Such a circuit arrangement, which is known from the Swiss Pat. No. 413,933, is to be used particularly in a rectifier circuit which is intended for the conversion of high voltages.
This prior art circuit arrangement has a high-frequency transmission signal, onto which the information of the control signals is amplitude modulated. The carrier frequency of the transmission signal is 1 MHz. In the absence of further data, the modulation involved here may be frequency as well as amplitude modulation. Tuned circuits are specifically used as the high-frequency receivers in the known circuit arrangement. The coils of the individual tuned circuit are inductively coupled to the coil of the high-frequency transmitter. Thus, near-field coupling is involved which is disadvantageous for high voltages: On the one hand, the mutual distance must be small, so that a firing signal of sufficient strength is available at the semiconductor valves, and on the other hand, the mutual distance must be large, so that no corona discharges occur. The contradictory requirements are an obstacle to a practical design of the prior art circuit arrangement with tunedcircuit coils.
It is an object of the invention to provide a circuit that is reliable and achieves interference-proof firing of the semiconductor valves, with a considerable distance between the high-frequency transmitter and the high-frequency receiver, if high voltages are present at the semiconductor valves.